"Very strange things are afoot at Fablehaven. Someone or something has released a plague that transforms beings of light into creatures of darkness. Seth discovers the problem early, but as the infectious disease spreads, it becomes clear that the preserve cannot hold out for long. In dire need of help, the Sorensons question where to turn. The Sphinx has always given sound advice, but is he a traitor? Inside the Quiet Box, Vanessa might have information...

When Kendra and Seth return to Fablehaven, they discover that Grandpa Sorenson has asked three specialists to protect the property from the Society of the Evening Star, a group determined to steal an artifact of great power from the preserve.

Since ancient times, the great demon prison Zzyzx has protected the world from the most dangerous servants of darkness, including Gorgrog, the Demon King. After centuries of plotting, the Sphinx is on the verge of recovering the five artifacts necessary to open the legendary prison. To thwart the Sphinx's designs and find a safe home for the five artifacts, Kendra, Seth, and the Knights of the Dawn must venture far beyond the walls of Fablehaven in...